Adding entities to a template
Adding an item or any other entity to a template is virtually identical to the same operation performed on a regular host. This is especially true for items. As you already know, item keys are the basic building blocks of the Zabbix monitoring pipeline and you don't have to specify any kind of address or interface when you create them, as Zabbix will take this kind of information from the host the item is assigned to. This means that when you create items for a template, you are effectively creating items for an ideal host that will be later applied to real ones, once you have linked the template to the hosts you want to monitor.
Templates, just like hosts, are essentially collections of items, triggers, and graphs. ...